Canada’s banking regulator wants mortgage default insurers to put more money between themselves and taxpayers, especially for mortgages they insure in riskier cities.

The new rules,detailedtoday by OSFI, will force government-backed insurers to bolster their capital on mortgages in certain areas. Effective January 1, 2017, this could make mortgages more expensive for insurers and consumers alike.

“When house prices are high relative to borrower incomes, the new framework will require that more capital be set aside,” said Superintendent Jeremy Rudin.

In a report today, BMO Capital Markets referred to these changes as “modestly tougher capital requirements.” It said that “through a phase-in mechanism” the new rules “essentially apply to new business only.”

You can bet your last basis point that insurers are already looking at ways to offset these new costs. Borrowers could be stuck with steeper premiums, higher interest rates and/or more rigid underwriting. That’s especially true if they have:

Lower credit scores

Higher loan-to-values

Longer amortizations.

I’m hearing insiders speculate that this could even lead to regional premium variations. So I asked OSFI if it’s possible that a borrower in Toronto might be asked to pay a higher insurance premium than a borrower in, say, London, Ontario. OSFI replied: “It is up to the institutions to determine how they will manage the new requirements.”

As of Q2, Toronto, Vancouver, Edmonton and Calgary would have exceeded OSFI’s valuation thresholds and forced insurers to cough up more capital on mortgages in those cities. OSFI is using census metropolitan areas (CMAs) to define the regional boundaries.

The following map shows Toronto’s CMA, for example. If regional variations came to reality, someone in Guelph, Barrie and Oshawa could pay smaller insurance premiums than borrowers in Toronto, Mississauga and Markham.

Genworth Canada, the country’s largest private insurer, is already setting expectations for higher premiums. In a statement today itsaid:

“The Company expects that the capital required for certain loan-to-value categories may increase and this could lead to a corresponding increase in premium rates. In addition, for those regions that are impacted by the supplementary capital, premium rates could also increase.”

CMHC reviews premiums annually. We wouldn’t be surprised if it announces higher premiums by the first few months in 2017 or before.

Even premiums on low-ratio mortgages may rise. That could be a problem for certain monoline lenders who depend on buying transactional insurance to fund (securitize) their mortgages. More expensive low-ratio premiums could put them at a further competitive disadvantage to big banks that don’t rely on low-ratio transactional insurance.

OSFI confirmed for us that, “The same calculation formulas will be used for all mortgages whether insured individually or as part of a portfolio.”

Rising premiums aren’t the only fallout here. It could also get incrementally tougher for some borrowers to get an insured mortgage. Insurers may now try even harder not to incur losses on mortgages that entail higher capital costs. That could mean marginally more declines and fewer guideline exceptions.

In some cases, however, insured mortgages might actually require less capital than today. OSFI says, “All else being equal, the capital requirement for mortgages associated with borrowers with better credit, and that pay their mortgages off quickly, will be lower. Also, under the new framework, mortgage insurers will no longer have to hold capital for mortgages that have been fully paid off.”